The whale shark, Rhincodon typus, is the largest fish known to exist. These gentle giants navigate the oceans, recognized by their unique pattern of light spots and stripes, which is unique to each individual shark. They are an ancient lineage, fascinating researchers and ocean enthusiasts alike.
Primary Diet
Whale sharks primarily consume some of the ocean’s smallest organisms. Their diet mainly consists of plankton, including microscopic phytoplankton and various zooplankton like copepods, krill, and crab larvae. They also feed on small nektonic life, such as jellyfish, small crustaceans, and schooling fish like anchovies, sardines, and mackerels, and consume fish eggs, especially during mass spawning events. Though they have numerous rows of tiny teeth, these are vestigial and not used for feeding. A juvenile whale shark can consume an estimated 21 to 45 pounds of plankton daily to sustain its growth and energy needs.
Filter Feeding Mechanism
Whale sharks employ a highly efficient filter-feeding strategy to process vast quantities of water for their minuscule prey. Unlike many other sharks, their broad mouth is positioned at the front of their head. As they feed, seawater enters their massive mouth cavity, which can span up to 1.5 meters wide, then passes through specialized gill rakers. These gill rakers, evolved into a mesh-like tissue, trap food particles as small as 1 millimeter while allowing filtered water to exit through the gill slits.
Whale sharks utilize two primary filter feeding methods: ram feeding and suction feeding. In ram feeding, the shark swims forward with its mouth open, forcing water and prey over its gill structures; this method is often used when prey density is lower. Suction feeding involves the shark actively opening and closing its mouth, creating negative pressure to gulp in large volumes of water and concentrated prey. This method can be particularly energy-intensive and is often employed when prey is densely aggregated, sometimes with the shark in a stationary or vertical position. Whale sharks also exhibit a “coughing” behavior, which helps clear particles from their filter pads.
Foraging Behavior and Habitats
Whale shark feeding habits influence their movements and habitat choices. They are highly migratory, found in tropical and warm-temperate seas with water temperatures typically above 21°C. Their migrations are driven by food availability, as they seek areas rich in plankton blooms or fish spawning events, often congregating in locations such as off the Yucatán Peninsula in Mexico or Ningaloo Reef in Western Australia during coral spawning. They typically forage near the ocean surface, where plankton and small fish are abundant, and though often solitary, they aggregate in large numbers when food sources are concentrated. Research suggests whale sharks use their sense of smell to detect chemical cues, like dimethyl sulfide, guiding them to productive feeding grounds.